This invention relates to radiotelephone communications systems and methods, and more particularly to terrestrial cellular and satellite cellular radiotelephone communications systems and methods.
Satellite radiotelephone communications systems and methods are widely used for radiotelephone communications. Satellite radiotelephone communications systems and methods generally employ at least one space-based component, such as one or more satellites that are configured to wirelessly communicate with a plurality of satellite radiotelephones.
A satellite radiotelephone communications system or method may utilize a single antenna beam covering an entire area served by the system. Alternatively, in cellular satellite radiotelephone communications systems and methods, multiple beams are provided, each of which can serve distinct geographical areas in the overall service region, to collectively serve an overall satellite footprint. Thus, a cellular architecture similar to that used in conventional terrestrial cellular radiotelephone systems and methods can be implemented in cellular satellite-based systems and methods. The satellite typically communicates with radiotelephones over a bidirectional communications pathway, with radiotelephone communication signals being communicated from the satellite to the radiotelephone over a downlink or forward link, and from the radiotelephone to the satellite over an uplink or return link.
The overall design and operation of cellular satellite radiotelephone systems and methods are well known to those having skill in the art, and need not be described further herein. Moreover, as used herein, the term xe2x80x9cradiotelephonexe2x80x9d includes cellular and/or satellite radiotelephones with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radiotelephone with data processing, facsimile and/or data communications capabilities; Personal Digital Assistants (PDA) that can include a radio frequency transceiver and a pager, Internet/intranet access, Web browser, organizer, calendar and/or a global positioning system (GPS) receiver; and/or conventional laptop and/or palmtop computers or other appliances, which include a radio frequency transceiver.
As is well known to those having skill in the art, terrestrial networks can enhance cellular satellite radiotelephone system availability, efficiency and/or economic viability by terrestrially reusing at least some of the frequency bands that are allocated to cellular satellite radiotelephone systems. In particular, it is known that it may be difficult for cellular satellite radiotelephone systems to reliably serve densely populated areas, because the satellite signal may be blocked by high-rise structures and/or may not penetrate into buildings. As a result, the satellite spectrum may be underutilized or unutilized in such areas. The use of terrestrial retransmission can reduce or eliminate this problem.
Moreover, the capacity of the overall system can be increased significantly by the introduction of terrestrial retransmission, since terrestrial frequency reuse can be much denser than that of a satellite-only system. In fact, capacity can be enhanced where it may be mostly needed, i.e., densely populated urban/industrial/commercial areas. As a result, the overall system can become much more economically viable, as it may be able to serve a much larger subscriber base. Finally, satellite radiotelephones for a satellite radiotelephone system having a terrestrial component within the same satellite frequency band and using substantially the same air interface for both terrestrial and satellite communications can be more cost effective and/or aesthetically appealing. Conventional dual band/dual mode alternatives, such as the well known Thuraya, Iridium and/or Globalstar dual mode satellite/terrestrial radiotelephone systems, may duplicate some components, which may lead to increased cost, size and/or weight of the radiotelephone.
One example of terrestrial reuse of satellite frequencies is described in U.S. Pat. No. 5,937,332 to the present inventor Karabinis entitled Satellite Telecommunications Repeaters and Retransmission Methods, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein. As described therein, satellite telecommunications repeaters are provided which receive, amplify, and locally retransmit the downlink signal received from a satellite thereby increasing the effective downlink margin in the vicinity of the satellite telecommunications repeaters and allowing an increase in the penetration of uplink and downlink signals into buildings, foliage, transportation vehicles, and other objects which can reduce link margin. Both portable and non-portable repeaters are provided. See the abstract of U.S. Pat. No. 5,937,332.
In view of the above discussion, there continues to be a need for systems and methods for terrestrial reuse of cellular satellite frequencies that can allow improved reliability, capacity, cost effectiveness and/or aesthetic appeal for cellular satellite radiotelephone systems, methods and/or satellite radiotelephones.
According to embodiments of the present invention, a satellite radiotelephone system can include a space-based component, a plurality of ancillary terrestrial components, and a plurality of radiotelephones. The space-based component can be configured to provide wireless radiotelephone communications using satellite radiotelephone frequencies. The plurality of ancillary terrestrial components can include a plurality of ancillary terrestrial component antennas configured to provide wireless radiotelephone communications using at least one of the satellite radiotelephone frequencies in a radiation pattern that increases radiation below the horizon compared to above the horizon. The plurality of radiotelephones can be configured to communicate with the space-based component and with the plurality of ancillary terrestrial components, and the radiotelephones can also include a GPS signal receiver/processor and a GPS mode filter configured to selectively suppress energy at and/or below (1575.42xe2x88x92xcex94) MHz, where 0 less than xcex94xe2x89xa616.42 MHz.
The GPS mode filter can be configured to suppress at least 10 dB of energy for at least one value of xcex94. More particularly, the GPS mode filter can be configured to selectively suppress at least 10 dB of energy at and/or below (1575.42xe2x88x92xcex94) MHz. The GPS mode filter can be further configured to suppress energy at frequencies less than (1575.42xe2x88x92xcex94) MHz, and xcex94 can be greater than at least 1 MHz. Accordingly, the GPS mode filter can be a high pass filter.
In addition, the radiotelephones can be further configured to suppress processing of GPS signals during intervals of time when actively communicating with the space-based component and/or one of the ancillary terrestrial components. The wireless radiotelephone communications can be processed without being subjected to the GPS mode filter.
The satellite radiotelephone frequencies can include a satellite downlink frequency band and a satellite uplink frequency band and GPS signals can be transmitted from GPS satellites over a GPS frequency band between the satellite downlink and uplink frequency bands. More particularly, the satellite downlink frequency band can include frequencies between 1525 MHz and 1559 MHz, and the satellite uplink frequency band can include frequencies between 1626.5 MHz and 1660.5 MHz. The GPS frequency band can include frequencies between 1559 MHz and 1605 MHz.
According to additional embodiments of the present invention, a radiotelephone can include a radio front end, a signal processor, and a GPS mode filter. The radio front end can be configured to provide wireless radiotelephone communications with a space-based component using satellite radiotelephone frequencies, to provide wireless radiotelephone communications with a plurality of ancillary terrestrial components using at least one of the satellite radiotelephone frequencies, and to receive global positioning satellite (GPS) signals from a plurality of global positioning satellites. The signal processor can be configured to determine a measure of location of the radiotelephone using GPS signals received at the radio front end when providing GPS mode operations and to process communications that are received at and/or transmitted from the radio front end when providing wireless radiotelephone communications. The GPS mode filter can be coupled between the radio front end and the signal processor and configured to filter GPS signals from the radio front end before being provided to the signal processor. More particularly, the GPS mode filter can be configured to suppress energy at and/or below (1575.42xe2x88x92xcex94) MHz, where 0 less than xcex94xe2x89xa616.42 MHz, and xcex94 can be greater than at least 1 MHz.
According to particular embodiments, wireless radiotelephone communications are not subjected to the GPS mode filter. The GPS mode filter can be configured to suppress at least 10 dB of energy at and/or below (1575.42xe2x88x92xcex94) MHz, and the GPS mode filter can be more particularly configured to suppress at least 10 dB of energy at (1575.42xe2x88x92xcex94) MHz and at frequencies less than (1575.42xe2x88x92xcex94) MHz. Accordingly, the GPS mode filter can be a high pass filter. Processing of GPS signals at the signal processor can be suppressed when actively providing radiotelephone communications with the space-based component and/or one of the ancillary terrestrial components.
The satellite radiotelephone frequencies can include a satellite downlink frequency band and a satellite uplink frequency band and GPS signals can be transmitted from GPS satellites over a GPS frequency band between the satellite downlink and uplink frequency bands. More particularly, the satellite downlink frequency band can include frequencies between 1525 MHz and 1559 MHz, and the satellite uplink frequency band can include frequencies between 1626.5 MHz and 1660.5 MHz. The GPS frequency band can include frequencies between 1559 MHz and 1605 MHz.
According to still additional embodiments of the present invention, satellite radiotelephone communications can be provided at a radiotelephone comprising a radio front end that is configured to provide wireless radiotelephone communications with a space-based component using satellite radiotelephone frequencies, that is configured to provide wireless radiotelephone communications with a plurality of ancillary terrestrial components using at least one of the satellite radiotelephone frequencies, and that is configured to receive global positioning satellite (GPS) signals from a plurality of Global positioning satellites. Energy can be suppressed at and/or below (1575.42xe2x88x92xcex94) MHz for GPS signals received from the radio front end (where 0 less than xcex94xe2x89xa616.42 MHz) during GPS mode operations, and a measure of location of the radiotelephone can be determined using the GPS signals having suppressed energy at (1575.42xe2x88x92xcex94) MHz during GPS mode operations. During wireless radiotelephone communications, communications that are received at and/or transmitted from the radio front end can be processed. More particularly, xcex94 can be greater than at least 1 MHz.
Processing communications that are received at and/or transmitted from the radio front end during wireless radiotelephone communications can include processing the communications without suppressing energy of the communications at and/or below (1575.42xe2x88x92xcex94) MHz. In addition, suppressing energy at and/or below (1575.42xe2x88x92xcex94) MHz can include suppressing at least 10 dB of energy at and/or below (1575.42xe2x88x92xcex94) MHz. More particularly, suppressing energy at (1575.42xe2x88x92xcex94) MHz can include suppressing at least 10 dB of energy at frequencies or (1575.42xe2x88x92xcex94) MHz and lower. Moreover, processing of GPS signals can be suppressed when actively providing radiotelephone communications with the space-based component and/or one of the ancillary terrestrial components.
The satellite radiotelephone frequencies can include a satellite downlink frequency band and a satellite uplink frequency band and GPS signals can be transmitted from GPS satellites over a GPS frequency band between the satellite downlink and uplink frequency bands. More particularly, the satellite downlink frequency band can include frequencies between 1525 MHz and 1559 MHz, and the satellite uplink frequency band can include frequencies between 1626.5 MHz and 1660.5 MHz. The GPS frequency band can include frequencies between 1559 MHz and 1605 MHz.